Gamma & BT.1886 explained. Lightspace users check in here - need your help! - Page 7 - AVS Forum
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post #181 of 200 Old 12-24-2013, 06:36 AM
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If you use bt1886, the relative curve will be off, simply because its a curve. With straight gamma your relative curve will be the same. I am not discussing the real world benefits or negatives of this, just trying to figure out if my (minimal) theoretical understanding is correct. This is not getting "hung up" on anything, it is trying to understand.
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post #182 of 200 Old 12-24-2013, 06:39 AM - Thread Starter
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Quote:
Originally Posted by ConnecTEDDD View Post

...so if their thay are using BT1886 then is 100% 2.4 Power Curve....

So let's say you know that they used a straight power curve of 2.4, and you have a display with a relatively high black level. Are you suggesting it's better to calibrate to a pure 2.4?
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post #183 of 200 Old 12-24-2013, 06:41 AM - Thread Starter
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Quote:
Originally Posted by Wouter73 View Post

If you use bt1886, the relative curve will be off, simply because its a curve. With straight gamma your relative curve will be the same. I am not discussing the real world benefits or negatives of this, just trying to figure out if my (minimal) theoretical understanding is correct. This is not getting "hung up" on anything, it is trying to understand.

Yes, the relative curve will be more "off", but perceptually it will be more "on".
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post #184 of 200 Old 12-24-2013, 06:41 AM
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Thanks smile.gif
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post #185 of 200 Old 12-24-2013, 06:56 AM
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Quote:
Originally Posted by spacediver View Post

Quote:
Originally Posted by ConnecTEDDD View Post

...so if their thay are using BT1886 then is 100% 2.4 Power Curve....

So let's say you know that they used a straight power curve of 2.4, and you have a display with a relatively high black level. Are you suggesting it's better to calibrate to a pure 2.4?

There is not something standard, so use any gamma value it provides you the better performance of your set.

I like 2.25 more to my KURO, but again it has to do with the movie you see.....

I'm not suggesting any gamma value..... save 2 different memories and swap when the movie starts...

If you have a TV with high black level, buy a better one!

We are talking about image fidelity here.

BT1886 for consumer sets need ''Working and not broken'' 10-Point Gamma Controls (with small steps of change; while you are using them), that by tweaking them to not produce other new problems to your image (banding etc.)


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post #186 of 200 Old 12-24-2013, 07:04 AM - Thread Starter
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Quote:
Originally Posted by ConnecTEDDD View Post

There is not something standard, so use any gamma value it provides you the better performance of your set.

Do you agree that if BT.1886 became standard, that there would be a standard "gamma" value?
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post #187 of 200 Old 12-24-2013, 07:04 AM
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Quote:
Originally Posted by ConnecTEDDD View Post

Guys, you can write posts for ages but you still never know what gamma is used for any movie, you don't know under what lighting conditions the mastering of each movie had performed also....

So apply 2 memories (using your display internal controls) or 3-4 different memories if you use external LUT Boxes and that's all!

I have 6 Memories here with my eeColor (2.2, 2.22, 2.25, 2.30, 2.35, 2.40) + KURO + Calibrated with Klein K-10A with LightSpace and some movies are not mastered so tight, others have poor shadow detail, others have rised black etc etc..

Am I doing something wrong? No... What ever gamma curve you follow ... if the movie is not mastered so well.... u can't do anything.....

(Expept to use some LightSpace Filters to reveal some extra shadow detail or lower the black level for a problematic movie.... like Carbon Ft Print is doing... wink.gif

Movies are mastered for blu-ray to be played everywhere, so they use something below 2.20-2.40......they are not mastered to be played only for 'batman cave' rooms....

Start your movie you want to watch and select on-the fly the memory that it fits better to your eyes and that all........

Thanks Ted,

So if I calibrate to 2.2 as well as BT.1886 it would hopefully suffice?
The coincidence is that they are my original Day / Night settings, however I may now be using them to evaluate the varying source as well.

Sorry Spacediver if my post is not exclusively about BT.1886 but I think everything is mixing together OK on your thread for me.
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post #188 of 200 Old 12-24-2013, 07:05 AM
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In the real world only people with an interest in calibration will take note of the black level, and get a display that has a decent one. People who are on a budget will most likely get a tv without 10 point gamma, so bt1886 will not be possible/very difficult for them.
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post #189 of 200 Old 12-24-2013, 07:15 AM
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With all the talk lately with gamma/black levels. I'm curious, what are black levels like in IMAX and other big cinemas?
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post #190 of 200 Old 12-24-2013, 07:16 AM - Thread Starter
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Quote:
Originally Posted by Wouter73 View Post

In the real world only people with an interest in calibration will take note of the black level, and get a display that has a decent one. People who are on a budget will most likely get a tv without 10 point gamma, so bt1886 will not be possible/very difficult for them.

If they don't have the ability to calibrate to BT.1886, they can always do the best they can. It's not like they'll be worse off compared to if the studio didn't use BT.1886.

And remember, a key benefit of BT.1886 is that it finally standardizes the power to 2.4, and this serves everyone better.

The whole nifty math part about changing the shape of the curve is only relevant when you're dealing with higher than reference level black levels. If you have an OLED or a nice plasma, then this won't be an issue.

But knowing that the exponent was mastered at 2.4 is a great step forward.
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post #191 of 200 Old 12-24-2013, 07:22 AM
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Quote:
Originally Posted by spacediver View Post

If they don't have the ability to calibrate to BT.1886, they can always do the best they can. I think a lot of folks here are forgetting that BT.1886 is more important on the consumer end than the studio end.

It's still very hard, as you can usually meet the 30/70/80% targets but 5 - 20 can end up darker because you have no control down there. Sometimes the top end can be lighter or darker in between the other targets you've closely nailed. It's one of the reasons I do straight line gamma with 2 point.
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post #192 of 200 Old 12-24-2013, 07:24 AM
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Quote:
Originally Posted by PE06MCG View Post

Quote:
Originally Posted by ConnecTEDDD View Post

Guys, you can write posts for ages but you still never know what gamma is used for any movie, you don't know under what lighting conditions the mastering of each movie had performed also....

So apply 2 memories (using your display internal controls) or 3-4 different memories if you use external LUT Boxes and that's all!

I have 6 Memories here with my eeColor (2.2, 2.22, 2.25, 2.30, 2.35, 2.40) + KURO + Calibrated with Klein K-10A with LightSpace and some movies are not mastered so tight, others have poor shadow detail, others have rised black etc etc..

Am I doing something wrong? No... What ever gamma curve you follow ... if the movie is not mastered so well.... u can't do anything.....

(Expept to use some LightSpace Filters to reveal some extra shadow detail or lower the black level for a problematic movie.... like Carbon Ft Print is doing... wink.gif

Movies are mastered for blu-ray to be played everywhere, so they use something below 2.20-2.40......they are not mastered to be played only for 'batman cave' rooms....

Start your movie you want to watch and select on-the fly the memory that it fits better to your eyes and that all........

Thanks Ted,

So if I calibrate to 2.2 as well as BT.1886 it would hopefully suffice?
The coincidence is that they are my original Day / Night settings, however I may now be using them to evaluate the varying source as well.

Sorry Spacediver if my post is not exclusively about BT.1886 but I think everything is mixing together OK on your thread for me.

Try any gamma curve/value that performes better to your eyes and you are happy with the results while you are watching your favorite movies.

It makes no sense to use Power Curve 2.4 or BT1886 if you are not satisfied with the results under your current display/setup/room conditions etc. the time your are watching your movies...

Each one single of us has a different understanding on how a reference picture looks like at our mind... There is not available a Gold Number of gamma value for all...
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post #193 of 200 Old 12-25-2013, 03:56 PM
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Quote:
Originally Posted by ConnecTEDDD View Post

@ Post-Production during Blu-Ray Mastering, if they use LED Displays (LED backlight goes off during the black measurement) so if their thay are using BT1886 then is 100% 2.4 Power Curve....
The LED's may turn off, but that doesn't mean the light coming from the black parts of the screen are zero, unless you are viewing it in a completely dark environment, with everything painted black, class 1 filtered air, and you're wearing a black ninja suite. [ And not even then - any light at all is going find it's way onto the screen and be reflected off to some degree. ]

But yes, for all practical purposes it's going to be at least as black as a CRT BVM.
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post #194 of 200 Old 12-25-2013, 04:04 PM
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Quote:
Originally Posted by Wouter73 View Post

In the real world only people with an interest in calibration will take note of the black level, and get a display that has a decent one. People who are on a budget will most likely get a tv without 10 point gamma, so bt1886 will not be possible/very difficult for them.

Whats classed as decent and bad black levels?
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post #195 of 200 Old 12-25-2013, 04:17 PM
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and you're wearing a black ninja suite

I think it's safe to say that Ted always wears a black ninja suit.
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post #196 of 200 Old 12-25-2013, 06:30 PM - Thread Starter
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I think it's safe to say that Ted always wears a black ninja suit.

right there with you smile.gif
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post #197 of 200 Old 12-25-2013, 11:25 PM
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Originally Posted by xvfx View Post

Whats classed as decent and bad black levels?

http://www.avsforum.com/t/1471147/comparison-of-black-levels

Not really sure, but this shows some good black levels. Now what is still considered "decent", I dont know.
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post #198 of 200 Old 12-26-2013, 04:16 AM
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A few of those sound nasty?... 037 to 0135. One as high as 165...
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post #199 of 200 Old 01-02-2014, 11:00 AM
 
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When it comes to the newest plasma TVs with extremely deep blacks, like my friend's ZT60, does it still make sense to use BT gamma? Even power law 2.2 (not 2.4) makes blacks way too dark on a ZT60. Power law 2.2 actually fully crushes black levels 1 and 2 on my monitor with 0.17 cd/m^2 black point level. Unlike power law 2.2, BT gamma also darkens the 254th gray/white shade, the shade that can be easily clipped.

Is using APL windows to adjust gamma any different when it comes to BT gamma?
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post #200 of 200 Old 01-02-2014, 11:06 AM
 
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Quote:
Originally Posted by Wouter73 View Post

http://www.avsforum.com/t/1471147/comparison-of-black-levels

Not really sure, but this shows some good black levels. Now what is still considered "decent", I dont know.

So, you can generally say that BT gamma is for CCFL and LED LCDs for sure, but not necessarily for new plasma TVs. I think 0.04 cd/m^2 is a great black for a 4 year old TV I have, which does not crush any blacks with power law 2.2 gamma, but it makes it hard to see, unless you stare at the scene for a few seconds with all the light around you turned off. With light turned on, I have to up my black to at least 0.06 cd/m*2 to see all the details in black scenes.
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